1. Field of the Invention
The present invention is directed to a device for radiation temperature measurement of molten masses in a vacuum.
2. Description of Related Art
When molten samples, particularly metals, are subjected to temperature measurement in a vacuum, a problem occurs in that material of the sample, when being in a vaporous state, deposits on the wall of the vacuum chamber or on the window of the used pyrometer. Due to vaporization, the initially radiation-permeable member becomes impermeable to radiation after a short time and thus cannot be used for further pyrometric measurement.
A device for radiation temperature measurement of molten masses in a vacuum is known from Japanese laid-open patent application 60-57224, published Aug. 2, 1985. In this device, screen plates having tiny holes are mounted before the pyrometer, through which holes the radiation issuing from the molten mass can reach the pyrometer on a straightlined path. These screens have been provided to prevent vapor from penetrating to a window arranged before the pyrometer and from depositing thereon. Such a combination of screens cannot preclude the depositing of vapor on the observation window for a long time because a linear path for the evaporated particles is permanently open.
As known from German Patent 473 064 and U.S. Pat. No. 4,650,318, protection of lenses against deposition of particles can be obtained by generating gas streams before the lens for carrying these particles along. In vacuum chambers, however, such gas streams are undesired since they would impair the vacuum.
It is an object of the present invention to improve a device for radiation temperature measurement of molten masses in a vacuum in such a manner that vapor particles are more effectively kept off of the optical component or window arranged in the radiation path in the position nearest to the molten mass, so that the possible observation period is extended.
The device of the invention is also adapted for pyrometry of substances subliming in a vacuum. The device can be used for pyrometry of substances, no matter whether they are solid or fluid, which evaporate in a vacuum.